Re: Death by pointers.

Stefan Monnier <>
Mon, 25 Sep 1995 10:13:30 GMT

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Related articles
[2 earlier articles]
Re: Death by pointers. (1995-09-06)
Re: Death by pointers. (1995-09-11)
Re: Death by pointers. (1995-09-12)
Re: Death by pointers. (1995-09-12)
Re: Death by pointers. (1995-09-13)
Re: Death by pointers. (John Carter) (1995-09-23)
Re: Death by pointers. (Stefan Monnier) (1995-09-25)
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Newsgroups: comp.compilers
From: Stefan Monnier <>
Keywords: optimize, parallel
Organization: Ecole Polytechnique Federale de Lausanne
References: 95-09-099 95-09-061 95-09-120
Date: Mon, 25 Sep 1995 10:13:30 GMT

In article 95-09-120,
John Carter <> wrote:
] >to ensure better use of cache lines, but in C, it cannot be, because
] >some_array_ptr MIGHT be aliased to global. For large enough values of
] >m, the transformed piece of code is at least 3 times faster on a
] >high-performance workstation. Fortran rules usually allow this
] >transformation.
] Parallel programming can be really hairy if you go at it at fine time
] grain, but there is more than enough going on on a modern workstation
] to merely paralell process at a very high level.

Now tell us all how you want to recode the above-mentionned loop so as to
compensate the factor of 3 speed decrease by a factor of (at least) 3
parallelism. (since this is probably the inner loop, it probably eats up around
80% of the program's time. Don't bother parallelise the rest before you
parallelise the loop).


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